Metal working



1964 K. .1. THALLER ETAL 3,158,119

METAL WORKING Filed Jan. 18, 1961 2 Sheets-Sheet 1 in II II I I I AM KENNETH J. THALLER FRED '1'. CALLAHAN &

BY HAROLD WEISENSTEIN Nov. 24, 1964 K. J. THALLER ETAL 3,158,119

METAL WORKING 2 Sheets$heet 2 Filed Jan. 18, 1961 FIG. 5

FIG. 7

Lmvi m MLHS 01... 0A N m THAE mT s W 5 0. w I s T DD A M Em United States Patent Mel This invention relates to metal forming and more particularly to the utilization of explosive energy in the forming of protrusions on the surfaces of strain hardened sheet metals.

In the working of sheet metal structures it is common to form protrusions thereon for various applications. Typical of these applications is in dimpling or bowing out of a portion of the structure, as for example a portion which is adjacent an edge formed into a louver for various applications such as in housing for heat exchange structures and the like. A further example of such working is in fianging openings provided in such structures. Generally such working is performed on metal structures in their annealed state, with subsequent treatment to impart uniform physical properties, such as hardness, to the structure since the formed portion becomes work hardened in contrast to the unformed portions of the structure. In such application the Work structure is generally annealed to obtain uniform physical properties therein, and if desired, the entire structure can be subjected to uniform working to work harden the structure, as by explosives similar to the method described with respect to manganese steel in US. Letters Patent 2,703,297. However, such processes are not suitable to a similar Working of a strain hardened sheet metal structure Where it is undesired to soften the unformed portions of the strain hardened structure.

Accordingly, it is an object of this invention to shape strain hardened sheet metal structures with explosives.

Another object of this invention is to provide a novel process for deforming portions of strain hardened sheet metal structures adjacent an edge thereof.

A further object of this invention is to, provide a novel method for forming protrusions on a strain hardened sheet metal structure adjacent an edge thereof.

A still further object of this invention is to provide a novel method for forming flanged openings in a strain hardened sheet metal structure.

Other objects and advantages will become more apparent from the following description and drawings in which:

FIGURE 1 is a perspective view of a strain hardened sheet metal structure utilized in illustrating one embodiment of this invention;

FIGURE 2 is a partial elevational view in section of a means for the processing the strain hardened sheet of FIGURE 1 in accordance with the said one embodiment of this invention;

FIGURE 3 is a partial elevational view in section illustrating the resultant configuration formed of a strained sheet metal structure when processed in accordance with the said one embodiment of this invention;

FIGURE 4 is a perspective view of a sheet metal structure utilized in illustrating another embodiment of this invention;

FIGURE 5 is an 'elevational view in section showing a means for processing a sheet metal structure of FIGURE 4 in accordance with this second embodiment of the invention;

FIGURE 6 is a perspective view of the sheet metal structure of FIGURE 4 processed in accordance with this second embodiment of this invention;

FIGURE 7 is a perspective view of another sheet metal structure for illustrating a still further embodiment of this invention; and

FIGURE 8 is an elevational view partly in section for illustrating the processing of the sheet metal structure of FIGURE 7 in accordance with this third embodiment of this invention.

Generally speaking the invention comprehends the forming of an integral protrusion on a surface of a strain hardened sheet metal element particularly adjacent an edge thereof by a novel method which includes annealing the portion of the element which is to be formed into the protrusion While retaining substantially all of the remainder of the element in its strain hardened condition. Subsequently thereto the annealed portion is then subjected to explosive forces of sufficient energy to move it into the desired configuration of the protrusion while simultaneously work hardening the portion to the desired strain hardened condition.

More specifically, with reference to the drawings, a

strain hardened sheet metal structure 1 is illustrated in FIGURE 1 for treatment in accordance with this invention in which a portion of the structure adjacent an edge is to be formed into a suitable protrusion. This portion of the metal may be adjacent an edge which defines the periphery of the structure, or the portion may be adjacent an edge 2 of a perforation 3 such as a slot, as for example portion 7 which is contained within the dotted line 4. This portion 7 is shown circumscribed by the dotted line 4 and the edge 2 of perforation 3, and is the portion of structure 1 which is to be formed into the protrusion shown shaded for purposes of clarification.

In accordance with this invention the shaded portion of structure I circumscribed by the dotted line 4 and edge 3 is suitably softened by any conventional manner, either electrically with heating elements, or it may be softened by a flame 5 of'a torch 6 in order to anneal it locally in such a manner to retain substantially the remainder of the structure I in its strain hardened condition. When the portion '7 of structure 1 has been annealed it is subjected to explosive forces of sufiicient energy to move portion 7 into the configuration desired for the protrusion while simultaneously work hardening portion '7 to the strain hardened condition desired therein. The amount of work hardening induced in portion 7 will be necessarily dependent on the relationship desired between it and the remainder of the structure, and accordingly the amount of explosives employed will be governed to some extent by the strain hardened condition desired and, as will be obvious, on the thickness and type of material worked, and on the amount of deformation desired. In this respect it is to be understood that reference to a sheet metal structure is utilized in a descriptive sense, and the structure may be of any thickness capable of deformation under explosive forces. The specific condition of this portion is thus contingent on the desired degree of hardness in portion 7, as for example whether portion 7 is to be softer than the remainder of the structure, whether it is to have the same degree of hardness, or Whether the induced strain hardened condition of portion 7 is to have a greater degree of hardness than the remainder of structure I.

The explosive forces utilized may be generated in any suitable manner either by direct application through a suitable force transmitting medium which moves portion 2 against a suitable die surface, or the explosive structure and die may be contained in a suitable combustion chamber. Preferably, the explosive forces are applied to sheet metal structure I through a fluid or liquid medium as shown in FIGURE 2, which illustrates a forming means which eliminates precautions heretofore required for sealing against leakage of a liquid medium.

Accordingly, as illustrated in FIGURE 2, the sheet metal structure 1 with the portion 7 of it suitably annealed is placed on a die 8 which is appropriately recessed at 9 tothe shape of the configuration which is desired to be imparted to the protuberance formed from the annealed portion 7. The sheet metal structure 1 may be secured against the displacement on die 8, by any suitable means such as a clamp assembly 10 which is comprised of a plate 11 secured to die 8 by a nut and bolt unit such as 12 with the plate suitably spaced for clamping by a shim 13. The explosive forces employed for working portion] of the sheet metal structure 1 are generated by an explosive l4 immersed in a suitable column of liquid 15 such as water wherein the explosive 14 may be initiated or detonated by a suitable means preferably with electrical energy applied through detonator lead wires 16 which also facilitate the positioning of the ex plosive 14 in the liquid medium.

In the embodiment now described, the liquid medium is contained within a suitable pliable envelope 17, made of polyethylene and like materialadapted to contain a liquid, with the envelope held in position by a retaining or supporting ring l made of any suitable material such as cardboard and the like, which has sufficient strength to support the envelope with the water disposed within it. The envelope may be secured to the cardboard liner 13 in any desired manner, as for example by folding the edges 19 of the envelope 17 over the top side of cardboard liner 1% whereat they may be attached by adhesive clamping and the like. When the above components are assembled, leads 16 are connected acrossa source of electrical energy, such as a battery, and the explosive 14 is detonated, whereupon the resultant forces are transmitted through the liquid medium 15 against portion '7 of structure 1 to move it with sufiicient energy against the defining surfaces of recess 9, or die 8, to form the desired configuration of the protuberanceon louver 2b and to work harden the worked structure to the desired strain hardened condition.

Although the preceding embodiment has been described relative to the Working of sheet-like or planar structures,

the invention is equally applicable to the working of hollow cylindrical or tubular members which are strain hardened irrespective of cross-sectional configuration. In this regard, although the invention is adapted to the working of circular, elliptical and polygonal tubular members such as triangular, rectangular, hexagonal and the like, the succeeding embodiment will he described relative to the forming of metal flanges about openings 21 providedin a cylindricaltubular member 22. As above, with respect to sheet metal structure 1, the portion of tubular member 22 which is to form the flanges about opening 21 is softened by localized annealing, with the annealed portions indicatedin FIGURE 4 as shaded areas 23 circumscribed by broken lines 24. Subsequent to annealing tubular member 22 is positioned within a cylindrical cavity 34 of a split die 25 provided with radial cavities 26having across-section corresponding with the desired cross-sectional configuration which is to be imparted to the flanges formed about openings 21. As illustrated inFl'GURE 5, the cavities 26 correspond in number to the openings of tubular member 22 and the cross-section ,of these cavities coextends the respective openings and annealed portion 23 of tubular member 22. As with the preceding embodiment, the explosive forces are generated by an explosive, 27 suspended in a liquid medium 28 contained in a pliable envelope 29 supported by a cardboard liner 3t). These, components, of this embodiment, are supported on a sheet of cardboard 31 and a rigid annular ring 32 which is in turn supported on l-be'arns 33. his to be, understood that other material may be utilized for the cardboard support 31 provided the specific material selected is of sufiicient strength to support the weight of the liquid medium 28. it is also to be understood that sizing of tubular member 22 against die 25 in conjunction with the formation of the flange is also contemplated within the invention.

In this regard, where sizing of tubular member 22 is also contemplated the diameter of the cylindrical cavity 34-, of die 25, will be somewhat larger than the outside diameter of the tubular member 22. Upon assembly of the various components, the lead wires 35 extending from the explosive 27 are suitably energized to release the explosive forces which are then transmitted through the liquid medium 28 with suflicient energy to size the member 22 against the die 25 and to move the annealed portions 23 outwardly through the radial cavities 26 of die 25 to the desired configuration of flanges 36 which are to be for-med about openings 21 of tubular member 22. As with the preceding embodiment, suflicient explosive is utilized to both deform the metal and "to work harden the structure into the desired strain hardened condition. g y

A typical application of this embodiment may be illustrated with reference to the formation or" flanges on a 22 inch, 0.13. cylindrical tube 27inches long fabricated of Aluminum Alloy 5052-H32 and having 3/ inch thick walls, with the blank having throughout a hardness of Rockwell F 70 to 72. Suitable holes are machined, or provided in any other suitable manner, in the cylindrical blank in the areas to be flanged which in this specific example comprise four circular openings of 12 inches in diameter with each opening equidistantly spaced about the periphery of the blank. The blank is then annealed,

as by a flame, around a marginal area circumscribing the periphery of each opening with'the area being approximately equal in Width to the length of the flange to be formed, in this example 2 inches. A test for hardness of this annealed portion, after softening, gave readings of Rockwell F 43 to 45. Thereafter the cylindrical blank was positioned in a die similar to that shown in FIGURE 5 with 225 grains of a 40% gelatin dynamite explosive immersed in the liquid medium. Upon detonation of the explosive, the cylindrical blank was sized to a 22 CD. with flanges of 2 inches in length formed aboutopenings 12 inches in diameter. Hardness testing after explosive forming in accordance withthis invention about the body and flange of the resultant structure gave readings of Rockwell F 73 to 77. Of course it will be understood that greater degrees of strain hardening can be obtained with increased quantities of explosives. Conversely, less strain hardeningcan be induced in the worked portions with smaller quantities of explosives.

Although the preceding embodiments have been described relative to the formation of protuberances in a single step, the invention also contemplates multi -st a ge forming of the protuberances with intermittent softening of the portion of the blank which is formed into the protuberances, or from blanks having portions thereof deformed into an intermediate configuration of the ultimate shape desired for the protuberances. Typical of this latter embodiment is the tubular blank 37 having openings 38 partially flanged at 39. As above, the shaded portion 40 of blank 37 issoftened by suitable localized annealing whereupon the tube is positioned in a cylindrical cavity of a split die 42 having lateral cavities 43 extending and communicating with the cylindrical cavity. Thereafter, a liquid medium 44 disposed in an annular pliableenvelope 45 is disposed around and adjacent the partially formed flange 39 with the envelope and medium supported by an annular arrangement of cardboard liners. The liner is suitably dimensioned to permit the envelope 45 to droop below it about the partial flange 39. The forming force for completing the erection of the flanges is obtained by a series of explosives 48 disposed peripherally in liquid medium 44. The amount of explosive employed will again be that necessary to generate sufl'icient forces to move the partial flanges 3? radially outward of the tube 37 against the defining walls of lateral cavities 43 to form the configuration desired for the flanges about the openings of tube 37 and to impart to it the desired strain hardened condition.

Although the invention has been described with reference to specific materials, embodiments, and details, various modifications and changes, within the scope of the invention, will be apparent to one skilled in the art and are contemplated to be embraced within the invention.

What is claimed is:

1. A method for forming an integral annular flange extending from the surface of a uniformly thick strain hardened sheet metal element comprising forming an opening through said element adjacent the portion thereof which is to be formed into said flange with said portion circumscribing and abutting the periphery of said opening and being of the same thickness as the remainder of said element, annealing said portion while retaining substantially all of the remainder of said element in said strain hardened condition, and subjecting said portion on the side thereof opposite said surface to suflicient explosive forces to move said portion into the desired configuration of said flange and to work harden said portion to the desired strain hardened condition.

2. The method of claim 1 wherein said forces are transmitted to said portion through a liquid medium disposed adjacent said portion.

3. The method of claim 2 wherein said medium is contained in a pliable envelope having its outer wall contiguous with said side at least in the area thereof peripheral to said portion.

4. The method of claim 1 wherein said element comprises a hollow cylinder.

5. The method of claim 4 wherein said cylinder is positioned in a bore of an enclosing die adjacent said surface and having a cavity extending laterally of said bore opposite said portion with said cavity having a crosssection corresponding to the desired cross-sectional configuration of said flange, and said bore having a crosssection corresponding to the desired cross-sectional configuration of said cylinder.

6. A method for forming an integral annular flange extending from the surface of a uniformily thick strain hardened sheet metal element comprising forming an opening through said element adjacent the portion thereof which is to be formed into said flange with said portion abutting and circumscribing the periphery of said opening and being of the same thickness as the remainder of said element, annealing said portion while retaining substantially the remainder of said element in said strain hardened condition, subjecting said portion on the side thereof opposite said surface to sufiiicient explosive forces to move said portion into an intermediate configuration of said flange, again annealing said portion while retaining substantially said remainder of said element in said strain hardened condition, and again subjecting said portion on said side to suificient explosive forces to move said portion into the desired configuration of said flange and to work harden said portion to the desired strain hardened condition.

7. The method of claim 6 wherein said forces are transmitted to said portion through a liquid medium disposed adjacent said portion.

8. The method of claim 6 wherein said element comprises a cylinder.

9. The method of claim 8 wherein said cylinder is positioned in a bore of an enclosing die adjacent said surface and having a cavity extending laterally of said bore opposite said portion with said cavity having a crosssection corresponding to the desired cross-sectional configuration of said flange, and said bore having a crosssection corresponding to the desired cross-sectional configuration of said cylinder.

10. A method of working a uniformly thick strain hardened sheet metal element having an opening extending therethrough with the portion of said element which abuts and circumscribes said opening bent transverse to a surface of said element into an intermediate configuration of a desired integral annular flange extending from said surface, annealing said portion while retaining substantially the remainder of said element in said strain hardened condition, and subjecting said portion on the side thereof facing said opening to suflicient explosive forces to move said portion into the desired configuration of said flange and to Work harden said portion-to the desired strain hardened condition.

11. A method for forming integral annular flanges extending from the surface of a uniformly thick strain hardened metal hollow cylinder comprising forming at least two spaced openings through the walls of said cylinder adjacent the portions thereof which are to be formed into said flanges With each of said portions circumscribing and abutting the periphery of their corresponding opening and being of the same thickness as the remainder of said cylinder, annealing said portions while retaining substantially the remainder of said cylinder in said strain hardened condition, and subjecting said portions on the side thereof opposite said surface to sufficient explosive forces to move said portion into their,

respectively, desired configuration of said flanges and to work harden said portions to the strain hardened condition desired in them.

12. The method of claim 11 wherein said cylinder is positioned in a bore of an enclosing die adjacent said surface and having a plurality number of cavities corresponding to the number of said openings With each of said cavities extending laterally of said bore at points thereon opposite a corresponding opening of said cylinder, said cavities having a crosssection conforming to the desired cross-sectional configurations of said flanges corresponding thereto, and said bore having a cross-section conforming to the desired cross-sectional configuration of said cylinder.

References Cited by the Examiner UNITED STATES PATENTS 1,028,066 5/12 Smith 29-545 1,528,587 3/25 Thrachray 29-545 1,574,900 3/26 Kellogg 153-21 1,596,029 8/26 Spire 29-545 1,607,264 11/26 Ledwinka et al. 148-115 1,966,713 7/34 Flint.

2,290,965 7/42 Hodapp et al. 29-157 2,356,457 8/44 Gouda.

2,701,778 2/55 Vickery 148-145 XR 2,847,957 8/58 Watter et al. 113-44 2,977,917 4/61 Lyon 113-116 OTHER REFERENCES Explosives Form Space Age Shapes, Steel, Aug. 25, 1958, pages 82-86.

Production Explosive Forming on a Predictable Basis, Product Engineering, Apr. 20, 1959, pages 26-28.

Explosive Forming, American Machinist, vol. 103, No. 12, July 15, 1959, pages 127-138.

High Energy Rate Metal Forming, Interim Engineering Report No. 1, published Feb. 12, 1960, distributed by Office of Technical Services, Dept. of Commerce, pages 48-68.

MICHAEL V. BRINDISI, Primary Examiner.

NEDWIN BERGER, CHARLES W. LANHAM,

Examiners. 

1. A METHOD FOR FORMING AN INTEGRAL ANNULAR FLANGE EXTENDING FROM THE SURFACE OF A UNIFORMLY THICK STRAIN HARDENED SHEET METAL ELEMENT COMPRISING FORMING AN OPENING THROUGH SAID ELEMENT ADJACENT THE PORTION THEREOF WHICH IS TO BE FORMED INTO SAID FLANGE WITH SAID PORTION CIRCUMSCRIBING AND ABUTTING THE PERIPHERY OF SAID OPENING AND BEING OF THE SAME THICKNESS AS THE REMAINDER OF SAID ELEMENT, ANNEALING SAID PORTION WHILE RETAINING SUBSTANTIALLY ALL OF THE REMAINDER OF SAID ELEMENT IN SAID STRAIN HARDENED CONDITION, AND SUBJECTING SAID PORTION ON THE SIDE THEREOF OPPOSITE SAID SURFACE TO SUFFICIENT EXPLOSIVE FORCES TO MOVE SAID PORTION INTO THE DESIRED CONFIGURATION OF SAID FLANGE AND TO WORK HARDEN SAID PORTION TO THE DESIRED STRAIN HARDENED CONDITION. 